Animals can't reason or express themselves, naturally, so the litigation would be handled by human lawyers, acting as ventriloquists on behalf of the animal kingdom. Think Mister Ed the talking horse, crossed with Eliot Spitzer.

"Any animals that are entitled to bring suit would be represented by (human) counsel, who would owe guardian-like obligations and make decisions, subject to those obligations, on their clients' behalf," according to Sunstein. The Harvard legal scholar first proposed the argument in 2002.

Yet the Professor's proposal is fraught with practical difficulties. Ventriloquists have often seen their "animal" veer out of control: remember Rod Hull and Emu - or Bob Carrolgees and Spit The Dog? There would be chaos in the courtroom.
http://www.theregister.co.uk/2009/01/19/cass_sunstein_animal_rights/